Replication deficient influenza virus for the expression of heterologous sequences

ABSTRACT

The present invention covers a novel replication deficient influenza virus comprising a modified NS1 segment coding for a NS1 protein lacking a functional RNA binding domain and functional effector domain and a heterologous sequence inserted between the splice donor site and the splice acceptor site of the NS gene segment. Further the use of the virus as vector for expression of various proteins like chemokines, cytokines or antigenic structures is covered, methods for producing virus particles using said virus vector as well as its use for production of vaccines. Also a fusion peptide comprising part of the N-terminus of an NS1 protein and a signal sequence fused to the C-terminus of said NS1 peptide is covered.

The present invention covers a replication deficient influenza viruscomprising a modified NS1 segment coding for an NS1 protein lacking afunctional RNA binding domain and functional effector domain and aheterologous sequence inserted between the splice donor site and thesplice acceptor site of the NS segment. Said heterologous sequence canbe expressed either from the NS1 open reading frame or an open readingframe different from the NS1 open reading frame.

Further therapeutic preparations containing said replication deficientinfluenza virus and their use are covered as well as the process formanufacturing said virus.

The influenza virions consist of an internal ribonucleoprotein core (ahelical nucleocapsid) containing the single-stranded RNA genome, and anouter lipoprotein envelope lined inside by a matrix protein (M1). Thesegmented genome of influenza A and B virus consists of eight molecules(seven for influenza C) of linear, negative polarity, single-strandedRNAs which encodes eleven (some influenza A strains ten) polypeptides,including: the RNA-dependent RNA polymerase proteins (PB2, PB1 and PA)and nucleoprotein (NP) which form the nucleocapsid; the matrix membraneproteins (M1, M2 or BM2 for influenza B, respectively); two surfaceglycoproteins which project from the lipid containing envelope:hemagglutinin (HA) and neuraminidase (NA); the nonstructural protein(NS1) and the nuclear export protein (NEP). Influenza B viruses encodealso NB, a membrane protein which might have ion channel activity andmost influenza A strains also encode an eleventh protein (PB1-F2)believed to have proapoptotic properties.

Transcription and replication of the genome takes place in the nucleusand assembly occurs via budding on the plasma membrane. The viruses canreassort genes during mixed infections. Influenza virus adsorbs via HAto sialyloligosaccharides in cell membrane glycoproteins andglycolipids. Following endocytosis of the virion, a conformationalchange in the HA molecule occurs within the cellular endosome whichfacilitates membrane fusion, thus triggering uncoating. The nucleocapsidmigrates to the nucleus where viral mRNA is transcribed. Viral mRNA istranscribed and processed by a unique mechanism in which viralendonuclease cleaves the capped 5′-terminus from cellular heterologousmRNAs which then serve as primers for transcription from viral RNAtemplates by the viral transcriptase. Transcripts terminate at sites 15to 22 bases from the ends of their templates, where oligo(U) sequencesact as signals for the addition of poly(A) tracts. Of the eight viralRNA molecules of influenza A virus so produced, six are monocistronicmessages that are translated directly into the proteins representing HA,NA, NP and the viral polymerase proteins, PB2, PB1 and PA. The other twotranscripts undergo splicing, each yielding two mRNAs which aretranslated in different reading frames to produce M1, M2, NS1 and NEP.In most of influenza A viruses, segment 2 also encodes for a secondprotein (PB1-F2), expressed from an overlapping reading frame. In otherwords, the eight viral RNA segments code for eleven proteins: ninestructural and 2 nonstructural (NS1 and the recently identified PB1-F2)proteins.

The application of viral vectors for delivery of foreign proteins andbiologically active molecules is an attractive approach for genetherapy, treatment of cancer and prevention of infectious diseases.Influenza viruses are especially considered as potential vaccinevectors. In contrast to other vectors such as adenoviruses orretroviruses, influenza does not contain a DNA intermediate and istherefore not able to integrate into the host's chromosomes. There areseveral options to manipulate the influenza genome depending on thedesired aims and possibilities to produce recombinant viruses. Thesestrategies include the insertion of foreign proteins into the surfaceglycoproteins NA and HA (Muster T. et al., 1994, J. Virol., 68,4031-4034; Percy N. et al., 1994, J. Virol., 68, 4486-4492), thecreation of additional genomic fragments (Flick R and Hobom G., 1999,Virology, 262, 93-103; Watanabe T. et al., 2003, J. Virol., 77,10575-10583) and the manipulation of the non-structural NS1 protein(Ferko B. et al., 2001, J. Virol., 8899-8908; Takasuka N. et al., 2002,Vaccine, 20, 1579-1585). The influenza NS1 protein has severaladvantages as a target for engineering since it does not presumablyinterfere with the structure of the virions, but is synthesized in largequantities in infected cells and tolerates long insertions up to severalhundred nucleotides.

As NS1 is only expressed intracellulary and less exposed to the humoralarm of the immune system, the development of the immune response to theNS1 protein or to the proteins fused to NS1 is limited mainly to theinduction of CD8⁺ T cell immunity. Obviously, for the induction ofB-cell response or for the expression of biologically active molecules,efficient delivery of the recombinant protein to the cell surface isrequired.

Vaccination is presently seen as the best way to protect humans againstinfluenza. Annual human influenza epidemics (caused by influenza type Aor type B viruses) are manifested as highly infectious acute respiratorydisease with high morbidity and significant mortality. Vaccination isaccomplished with commercially available, chemically inactivated(killed) or live attenuated influenza virus vaccines. The concept of thecurrent live attenuated vaccine is based on the generation of atemperature sensitive attenuated “master strain” adapted to grow at 25°C. (cold adaptation). Live cold adapted (ca) and inactivated virusvaccine stimulate the immune system differently, yet in both cases lackof sufficient immunogenicity especially in elderly persons is one of themost important drawbacks in influenza vaccination. Although ca liveinfluenza virus vaccines are considered as sufficiently safe, the exactgenetic and molecular mechanisms of attenuation are not completelyunderstood. It is claimed that the nature of the safety of ca influenzavaccines is based on a large number of point mutations distributedacross the internal gene segments. However, only a small number ofmapped mutations localized in the polymerase genes are responsible forthe attenuation of ca virus strains that are unable to replicate atnormal body temperature (Herlocher, M. L., A. C. Clavo, and H. F.Maassab. 1996, Virus Res. 42:11-25; Herlocher, M. L., H. F. et al.,1993, Proc Natl Acad Sci USA. 90:6032-6036). In fact, the geneticstability of live vaccine strains are often questioned since virusesre-isolated from vaccinated hosts reveal additional point mutationswhich might eventually function as “suppressor” mutations causingenhanced replication properties and a possible loss of the temperaturesensitive phenotype of the revertant virus (Herlocher, M. L., H. F. etal., 1993, Proc. Natl. Acad. Sci. 90:6032-6036, Treanor, J., M. et al.,1994 J Virol. 68:7684-7688.)

Reflecting the potential risks of the ca live attenuated influenza virusvaccines and in view of the low stability often combined with lowexpression rate of foreign proteins in influenza virus vectors, there isstill a high demand to create a completely attenuated influenza virusvector inducing cellular and/or humoral immunogenicity and stablyexpressing high amounts of foreign proteins.

It has been surprisingly shown by the inventors that an influenza virusvector as developed according to the invention does fulfill these unmetdemands, i.e. providing an influenza virus vector that is of high safetydue to complete attenuation and which shows stable expression of foreigngenes inserted into the virus vector. Preferably, the foreign genes showhigh expression rates when inserted into the inventive virus vector.

Although various attempts have been made to overcome the issues of lowgenetic stability and low expression rate of proteins or peptides inattenuated virus vectors, none of these constructs have been efficientlysuccessful yet.

Kittel et al. (Virology, 2004, 324, 67-73) described an influenza Avirus consisting of an NS1 protein of 125 aa length (approx. one half ofthe wt NS1 protein) and expressing green fluorescence protein (GFP) fromthe NS1 reading frame, which was replicating in PKR knock out mice. Ininterferon competent cells the virus was not stably expressing GFP butthe virus was loosing its fluorescent activity due to the appearance ofvarious deletions within the GFP sequence.

A bicistronic expression strategy based on the insertion of anoverlapping stop-start codon cassette into the NS gene for expressingGFP was disclosed by Kittel et al. (2005, J. Virol., 79, 10672-10677).Although being genetically stable, the expression level of the GFP fromthis reading frame was significantly lower than that obtained from aninfluenza virus vector expressing GFP from the NS1 ORF (Kittel et al.,2004, see above).

Ferko et al. did not describe a replication deficient virus but a cainfluenza virus expressing human interleukin 2 (J. Virol., 2006,11621-11627). Yet, the genetic stability and safety of a cold adaptedvirus has to be questioned in view of the genetic structure leading totemperature sensitivity (Herlocher M. et al., Proc. Natl. Acad. Sci,1993, 90, 6032-6036). Additionally, the IL-2 expression levels were low.

The present invention relates to the development of a replicationdeficient influenza virus comprising a modified NS segment coding for anNS1 protein lacking a functional RNA binding domain and functionaleffector domain and a heterologous sequence inserted between the splicedonor site and the splice acceptor site of the NS1 gene segment.According to the invention the heterologous sequence can be expressedfrom the NS1 reading frame or from a separate open reading frame.

Although WO 07/016715 describes that influenza virus wherein the NS gene(sometimes referred to also as NS1 gene) comprises deletions and whereinthe virus can be used to express an immunostimulatory cytokine, there isno disclosure on the specific influenza vector which could successfullyexpress foreign proteins.

In contrast, the inventors have surprisingly shown that the heterologoussequences, which can be even larger than the natural intron, can bestably expressed at high levels from the NS segment if inserted betweena functional splice donor site and functional splice acceptor site,provided NS splicing efficiency is adjusted according to insert size.

This was neither shown nor indicated in WO 06/088481 and WO 01/64680.

According to a preferred embodiment of the invention, the functionalsplice donor site and the splice acceptor site of the NS gene segment isthe natural splice site.

According to the invention the heterologous sequences can be selectedfrom any biologically active proteins or peptides or antigenicstructures.

Antigenic peptides or proteins are characterized by comprising epitopeswhich can lead to immunomodulatory activities, like binding ofantibodies or antibody like structures or induction of cellular immuneresponses.

Preferably, proteins or peptides are selected from the group consistingof antigens, preferably bacterial antigens like ESAT6, growth factors,cytokines like interleukins, lymphokines and chemokines and fragments orderivatives thereof, more preferred from Mycobacterium tuberculosis,GM-CSF, CCL-3, CCL-20, interleukin 2, interleukin 15 or a fragment orderivative thereof.

The present invention further relates to therapeutic preparations,preferably vaccine preparations containing said replication deficientinfluenza viruses. Exemplarily these preparations can be used for theprevention and treatment of infectious diseases or cancer.

Further, methods for producing the inventive influenza viruses bytransfecting cell lines (e.g. Vero cells, MDCK cells etc.) andexpressing viral particles are disclosed.

FIGURES

FIG. 1 (a-j): Nucleic acid sequence of various vector constructs.

a: Sequence of the deINS1-IL-2-10 segment (SEQ ID No. 1)

b: Sequence of the deINS1-IL-2-11 segment (SEQ ID No. 2)

c: Sequence of the deINS1-IL-2-14 segment (SEQ ID No. 3)

d: Sequence of deINS1-IL2-13 segment (SEQ ID No. 4)

e: Sequence of deINS1-IL-2-21 segment (SEQ ID No. 5)

f: Sequence of deINS1-IL-2-17 segment (SEQ ID No. 6),

g: Sequence of deINS1-IL-15-21 segment (SEQ ID No. 7)

h: Sequence of deINS1-GM-CSF-21 segment (SEQ ID No. 8)

i: Sequence of deINS1-CCL-3-21 segment (SEQ ID No. 9)

j: Sequence of deINS1-CCL20-21 segment (SEQ ID No. 10)

k: Sequence of deINS1-ESAT-6s-21 segment (SEQ ID No. 67)

l: Sequence of deINS1-ESAT-6i-21 segment (SEQ ID No. 68)

m: Sequence of deINS1-IL2-23 segment (SEQ ID No. 78)

n: Sequence of deINS1-IL2-24 segment (SEQ ID No. 79)

FIG. 2: Schematic representation of the influenza A wild-type NS segmentand the three chimeric IL-2 NS segments deINS1-IL-2-10 anddeINS1-IL-2-11 and deINS1-IL-2-14.

FIG. 3: Human IL-2 levels in supernatants from Vero cells infected withGHB-IL-2-10, GHB-IL-2-11 or GHB01.

FIG. 4: RT-PCR analysis of the NS segment after five passages on Verocells

FIG. 5: Human IL-2 levels in supernatants from Vero cells infected withGHB-IL-2-11, GHB-IL-2-13, GHB-IL2-14 and GHB-IL2-21.

FIG. 6: Amino acid sequence of wt influenza virus PR8 NS1

FIG. 7: deINS1-IL-2 mRNA splicing can be altered by either modifying thesequence surrounding the splice donor site or the sequences 5′ to thesplice acceptor site.

FIG. 8: Schematic IL-2 expression construct. The ORF of the truncatedNS1 consists of nucleotides 45-158; the human IL-2 ORF consists ofnucleotides 161-619; the 5′ intron boundary is between nucleotides 77and 78; the 3′ intron boundary is between nucleotides 657 and 658.

FIG. 9: Nucleotide sequence of ΔNS1-38IL2 (SEQ ID No. 77).

The invention provides replication-deficient influenza virusescomprising a modified NS segment coding for a NS1 protein comprising atleast one amino acid modification within positions 1 to 73 resulting incomplete lack of its functional RNA binding and at least one amino acidbetween position 74 and the carboxy-terminal amino acid residue,specifically until amino acid position 167, resulting in complete lackof its effector function and a heterologous sequence between afunctional splice donor site and functional splice acceptor siteinserted in the NS gene segment.

Preferably the influenza virus is derived from influenza A virus,influenza B virus or influenza C virus. Vectors based on or derived fromInfluenza A or influenza B virus sequences are preferred.

The replication deficient influenza virus according to the invention canbe used as viral vector for immunization against any pathogens orantigenic structures to induce an immune response against theheterologous structures expressed by said viral vector. The immuneresponse can comprise a cellular immune response and/or a humoral immuneresponse. By using heterologous sequences expressing immunomodulatingproteins or peptides, the immune response towards the influenza viruscan be further boosted, resulting in an improved influenza vaccineformulation. This is especially relevant for vaccination of elderly orimmunosuppressed individuals.

The virus selected for use in the invention comprises a modified NS geneleading to an influenza virus that is attenuated, i.e. it is infectiousand can replicate in vivo in interferon deficient cells or cell systemsbut does not replicate in interferon competent cells. According to theinvention the term “replication deficient” is defined as replicationrate in interferon competent host cells that is at least less than 5%,preferably less than 1%, preferably less than 0.1% than wild typeinfluenza virus as determined by hemagglutination assay, TCID50 assay orplaque assay as well known in the art.

The NS gene segment according to the invention must contain functionalsplice donor and splice acceptor sites.

According to a specific embodiment of the invention, the influenza genesegments can be derived from different influenza strains, eitherpandemic or interpandemic ones. This can result in reassorted influenzaviruses which combine the genes for the surface glycoproteinshemagglutinin (HA) and/or neuraminidase (NA) of actual interpandemicviruses with five or six or seven RNA segments coding for other proteinsfrom the attenuated master strain (6/2 combination) or 7/1 reassortantsor 5/3 reassortants containing HA, NA and M segments of a circulatingstrain respectively.

The inventors have used a reverse genetics system on Vero cells fordeveloping reassortants and/or expression of modified influenza virusstrains. The technology is already well known in the art (Pleschka S. etal., 1996, J. Virol., 70(6), 4188-4192, Neumann and Kawaoka, 1999, Adv.Virus Res., 53, 265-300, Hoffmann et al. 2000, Proc Natl Acad Sci USA.97:6108-13). Alternatively, the technology based on RNPs as described byEnami and Enami (J. Virol, 2000, 74,12, pp. 5556-5561) can be used fordeveloping reassortants.

The NS1 protein of influenza A virus is a multifunctional protein thatconsists of approximately 230 amino acids and is early and abundantlysynthesized in infection. It counters cellular antiviral activities andis a virulence factor. By the activity of its carboxy terminal region,the NS1 protein is able to inhibit the host mRNA's processingmechanisms. Second, it facilitates the preferential translation of viralmRNA by direct interaction with the cellular translation initiationfactor. Third, by binding to dsRNA and interaction with putativecellular kinase(s), the NS1 protein is able to prevent the activation ofinterferon (IFN−) inducible dsRNA-activated kinase (PKR),2′5′-oligoadenylate synthetase system and cytokine transcriptionfactors. Fourth, the N terminal part of NS1 binds to RIG-I and inhibitsdownstream activation of IRF-3, preventing the transcriptional inductionof IFN-β. Therefore the NS1 protein inhibits the expression of IFN-α orIFN-β genes, delays the development of apoptosis in the infected cells,and prevents the formation of the antiviral state in neighbouring cells.Influenza viruses containing modifications within the NS1 protein areknown in the art. For example, WO 99/64571 describes the complete knockout of the NS gene segment, WO 99/64068 discloses various NS genesegments that have been partially deleted, yet none of the describedmodifications disclose an influenza virus vector according to thepresent invention.

According to the present invention the modification within the NS1protein can be a deletion, an insertion or substitution of at least oneamino acid resulting in a replication deficient influenza virus.

Preferably the modified NS1 protein comprises a deletion of at least 50%of the NS1 amino acids, preferably of at least 70%, more preferably ofat least 90%.

Alternatively, the functionality of the NS1 protein can be completelydiminished.

The NS1 protein of the influenza virus vector according to the inventionlacks the functional RNA binding domain. The primary function of thisdomain located at the amino end of the NS1 protein (amino acids 1-73,the wild type amino acid sequence is attached as SEQ ID No. 80) isbinding dsRNA and inhibiting the 2″5″oligo (A) synthetase/RNase Lpathway (Min J. et al., Proc. Natl. Acad. Sci, 2006, 103, 7100-7105,Chien et al., Biochemistry. 2004 Feb. 24; 43(7)1950-62) as well as theactivation of a cytoplasmic RNA helicase, RIG-I, retinoic acid-inducibleprotein I (Yoneyama M. et al., Nat. Immunol., 2004, 5, 730-737).

Lack of a functional RNA binding domain is defined according to thepresent invention as complete lack of dsRNA binding ability leading toan influenza virus that does not replicate in interferon competentcells.

According to the invention the effector domain of the NS1 protein ofinfluenza virus vector is not functional. The effector domain interactswith cellular proteins to inhibit mRNA nuclear export. The effectordomain is located at the C-terminal part of the NS1 protein. Accordingto Schultz et al. the effector domain is specifically located betweenamino acid residues 117 and 161, other literature locates the effectordomain between 134 and 161. The NS1 effector domain can be completely orpartially deleted as well as amino acids can be substituted or insertedand the remaining effector domain can be tested for functionality asdescribed in the art (Schultz-Cherry S. et al., J. Virol., 2001,7875-7881).

According to the invention the C-terminal amino acids relevant foreffector binding activity are modified to inhibit effector function.Specifically amino acids at positions 74 to 230, more specifically aminoacids at positions 116 to 161, more specifically at positions 134 to 161are modified. According to a preferred embodiment, the modification is adeletion of said amino acids.

The heterologous sequence according to the present invention can be anybiologically active protein or peptide or antigenic structure.

For example, antigenic structures can be proteins or carbohydratestructures which can be recognized by the immune system, e.g. antibodiesor antibody-like structures can bind to these structures. These epitopestructures can contain signal peptides or can be directly linked to themodified NS1 protein. For example, foreign epitope structures can bederived from other pathogens, from tumor associated antigens orretroviral epitopes expressed on the surface of tumour cells.Carbohydrate antigens are often of particularly weak immunogenicity.Their immunogenicity can be improved by conjugating the carbohydrate toa protein carrier. Proteins or peptides can also be linked totransmembrane domain sequences preferably containing stretches ofhydrophobic amino acids or other leader sequences known to be needed fortransporting the protein/peptide through the cellular membrane barriers.Transmembrane domain usually denotes a single transmembrane alpha helixof a transmembrane protein. An alpha-helix in a membrane can be foldedindependently from the rest of the protein, similar to domains ofwater-soluble proteins. A transmembrane domain can be anythree-dimensional protein structure which is thermodynamically stable ina membrane. This may be a single alpha helix, a stable complex ofseveral transmembrane alpha helices, a transmembrane beta barrel, abeta-helix of gramicidin A, or any other structure.

Transmembrane helices are usually about 20 amino acids in length,although they may be much longer or shorter.

For example these could be HA transmembrane sequences or any other knownviral transmembrane domains.

The biologically active protein used according to the invention cancomprise a signal peptide. The signal peptide can be any signal sequencebeing either a naturally occurring signal sequence or a synthetic one.For example it can be the naturally existing signal sequence of theheterologous sequence. Alternatively, it can also be derived from anantibody, preferably from an Ig kappa chain, more preferably from Igkappa signal peptide. Preferably, the Ig kappa chain is derived frommouse Ig kappa chain.

According to a preferred embodiment of the invention the heterologoussequence expresses cytokines or chemokines or fragments or derivativesthereof.

Cytokines are small secreted proteins which mediate and regulateimmunity, inflammation and hematopoiesis. The largest group of cytokinesare those which promote proliferation and differentiation of immunecells. Included within this group are interleukins, which are cytokinesproduced by leukocytes, and interferons, which may be produced by avariety of cell types.

Interferons (IFN) are a family of naturally occurring glycoproteinsproduced by cells of the immune system of vertebrates, includingmammals, birds, reptiles and fish, in response to challenge by agentssuch as bacteria, viruses, parasites and tumour cells. In humans thereare three major classes of interferons. The type I interferons include14 IFN-alpha subtypes and single IFN-beta, omega, kappa and epsilonisoforms. Type II interferons consist of IFN-gamma and a recentlydiscovered third class consists of IFN-lambda with three differentisoforms.

Th1 cells secrete mainly IL-2, IFN-γ, and TNF-β, whereas Th2 cells whichare relevant in humoral immune responses secrete cytokines such as IL-4,IL-5, and IL-10. Th2-type cytokines mediate delayed typehypersensitivity responses against intracellular pathogens and inhibitthe Th1 responses.

Chemokines, originally derived from chemoattractant cytokines, actuallycomprise more than 50 members and represent a family of small,inducible, and secreted proteins of low molecular weight (6-12 kDa intheir monomeric form) that play a decisive role duringimmunosurveillance and inflammatory processes. Depending on theirfunction in immunity and inflammation, they can be distinguished intotwo classes. Inflammatory chemokines are produced by many differenttissue cells as well as by immigrating leukocytes in response tobacterial toxins and inflammatory cytokines like IL-1, TNF andinterferons. Their main function is to recruit leukocytes for hostdefence and in the process of inflammation. Homing chemokines, on theother hand, are expressed constitutively in defined areas of thelymphoid tissues. They direct the traffic and homing of lymphocytes anddendritic cells within the immune system. These chemokines, asillustrated by BCA-I, SDF-1 or SLC, control the relocation andrecirculation of lymphocytes in the context of maturation,differentiation, activation and ensure their correct homing withinsecondary lymphoid organs.

According to the present invention it has been shown that biologicallyactive cytokines or chemokines or derivatives or fragments thereof canbe stably and efficiently expressed using an open reading framedifferent from the ORF expressing the NS1 protein. Alternativelyadditional leader sequences other than the natural signal peptides canbe fused to the cytokines or chemokines which may further supportefficient secretion of the protein and show a highly efficient inductionof immune response in vivo.

Surprisingly, chemokines and cytokines can also be efficiently expressedwhen the amino acid sequence corresponding to the maturecytokine/chemokine is fused to a part of the NS1 protein via an aminoacid sequence acting as a signal peptide , For example, this can be apart of the mouse IgKappa signal peptide.

According to the present invention the heterologous sequence preferablycodes for interleukin 2 (IL-2) or a fragment or derivative thereof. IL-2comprises secretory signal sequences and is an immunomodulatory, T-cellderived molecule required for the clonal expansion of antigen-activatedT-cells. The secretion of IL-2 by CD4+ T lymphocytes has multiplebiological effects, such as the induction of proliferation of T-helperand T-killer cells and the stimulation of T-cells to produce othercytokines. Furthermore, IL-2 can also activate B-cells, NK cells andmacrophages. When IL-2 is expressed from recombinant viruses infectingnon-lymphoid cells, its secretion could significantly decrease thepathogenesis of viral infection and modify the immune response. It isalso known that IL-2 acts as immune adjuvant.

According to the present invention any fragment or derivative of thecytokines and chemokines is included that is still biologically active,i.e. shows immunomodulatory activities.

Alternatively, the cytokines/chemokines can also be selected from thegroup consisting of IL-15, GM-CSF, CCL3 or CCL20 or derivatives orfragments thereof.

Alternatively, it can be also any epitope or immunomodulatory regionderived from Mycobacterium tuberculosis, for example ESAT-6.

Alternatively the heterologous sequences can also comprise chimericproteins being cytokines or chemokines or fragments or derivativesthereof fused to antigenic proteins or antigenic peptides. Fusion can beeither directly or via peptide linker sequences having a length of atleast 4 amino acids, preferably at least 5 amino acids. For example, thelinker sequences according to the invention are GGGS or GGGGS.

Examples for IL-2 chimeric proteins are known in the art. Exemplarily,this could be IL-2-PE40 (wherein PE is Pseudomonas exotoxin A),DAB389-IL-2 (where DAB is diphtheria toxin) or IL-2 Bax (wherein Bax isa proapoptotic protein of human origin) (Aqeilan R. et al., Biochem. J.,2003, 129-140).

According to the present invention the nucleotide sequences of theheterologous sequences which are introduced into the replicationdeficient influenza vector show at least 80% identity with their nativesequences, preferably at least 85% identity, more preferred at least 90%identity. Any optimization of the nucleotide sequence in view of codonusage is included thereby.

Alternatively, the heterologous sequence can comprise B-cell orT-cell-epitopes, for example a B cell epitope from influenzahemagglutinin (HATB), for example the A loop epitope from the influenzavirus hemagglutinin (HA) or parts thereof, or peptides representing oneof the immunodominant epitopes of HA corresponding to amino acidsequence 150 to 159 (Caton et al., 1982, Cell, 417-427).

The epitope can also be derived from melanoma-associated endogenousretrovirus (MERV) as described in WO06/119527. It can be an epitopederived from the gag, pol or env protein of the virus, preferably fromenv. Especially, it can be one or more of the following peptides:EMQRKAPPRRRRHRNRA (SEQ ID. No 12); RMKLPSTKKAEPPTWAQ (SEQ ID. No 13);TKKAEPPTWAQLKKLTQ (SEQ ID. No 14); MPAGAAAANYTYWAYVP (SEQ ID. No 15);PIDDRCPAKPEEEGMMI (SEQ ID. No 16); YPPICLGRAPGCLMPAV (SEQ ID. No 17);YQRSLKFRPKGKPCPKE (SEQ ID. No 18); FRPKGKPCPKEIPKESK (SEQ ID. No 19);GKPCPKEIPKESKNTEV (SEQ ID. No 20); GTIIDWAPRGQFYHNCS (SEQ ID. No 21);RGQFYHNCSGQTQSCPS (SEQ ID. No 22); DLTESLDKHKHKKLQSF (SEQ ID. No 23);PWGWGEKGISTPRPKIV (SEQ ID. No 24); PKIVSPVSGPEHPELWR (SEQ ID. No 25);PRVNYLQDFSQRSLKF (SEQ ID. No 26); RVNYLQDFSYQRSLKFR (SEQID. No 27);VNYLQDFSYQRSLKFRP (SEQ ID. No 28); VNYLQDFSYQRSLKFRSP (SEQ ID. No 29);NYLQDFSYQRSLKFRPK (SEQ ID. No 30); YLQDFSYQRSLKFRPKG (SEQ ID. No 31);LQDFSYQRSLKFRPKGK (SEQ ID. No 32); QDFSYQRSLKFRPKGKP (SEQ ID. No 33);DFSYQRSLKFRPKGKPC (SEQ ID. No 34); FSYQRSLKFRPKGKPCP (SEQ ID. No 35);SYQRSLKFRPKGKPCPK (SEQ ID. No 36); YQRSLKFRPKGKPCPKE (SEQ ID. No 37);QRSLKFRPKGKPCPKEI (SEQ ID. No 38); RSLKFRPKGKPCPKEIP (SEQ ID. No 39);SLKFRPKGKPCPKEIPK (SEQ ID. No 40); LKFRPKGKPCPKEIPKE (SEQ ID. No 41);KFRPKGKPCPKEIPKES (SEQ ID. No 42); FRPKGKPCPKEIPKESK (SEQ ID. No 43);RPKGKPCPKEIPKESKN (SEQ ID. No 44); PKGKPCPKEIPKESKNT (SEQ ID. No 45);KGKPCPKEIPKESKNTE (SEQ ID. No 46); GKPCPKEIPKESKNTEV (SEQ ID. No 47);KPCPKEIPKESKNTEVL (SEQ ID. No 48); PCPKEIPKESKNTEVLV (SEQ ID. No 49);CPKEIPKESKNTEVLVW (SEQ ID. No 50); PKEIPKESKNTEVLVWE (SEQ ID. No 51);SYQRSLKFRPKGKPCPKEIP (SEQ ID. No 52).

According to an alternative embodiment of the invention the heterologoussequence is expressed from an open reading frame (ORF) different fromthe NS1 ORF. Another method for generating a second ORF can be achievedby incorporation of an internal ribosome entry site element(Garcia-Sastre A., et al., 1999, J. Virol., 75, 9029-9036) or doublingof influenza virus promoter sequences (Machado A. et al., 2003,Virology, 313, 235-249).

According to the present invention it has been surprisingly shown thateven if the first approx. 12 amino acids of the NS1 protein are stillpresent, secretion of the heterologous sequence is not prohibited

Therefore, according to the present invention, the virus vector cancontain at least 10 amino acids, preferably up to 30, preferably up to20, preferred up to 14 amino acids of the N-terminus of the NS1 proteinand a signal peptide or part thereof fused to the NS1 C-terminus. TheC-terminal signal sequence is preferably present in case the NS1 proteincontains not more than 30 amino acids of the N-terminus.

By using this specific construct, i.e. the fusion of a signal peptide orpart thereof with said N-terminal amino acids of the NS1 protein, the soderived NS1 protein can be functionally modified to act as a signalpeptide. Expression of heterologous sequences by said fusion peptidescan increase the secretory characteristics of said heterologoussequences.

According to a preferred embodiment of the invention the translation ofthe NS1 protein is terminated by at least one stop codon and expressionof said heterologous sequence is reinitiated by a start codon. Forexample, a stop-start cassette having the sequence UAAUG (SEQ ID. No 53)can be inserted into the influenza A virus NS gene coding sequencefollowed by the insertion of the heterologous sequence. In view of theshort Stop-Start codon sequence and the limited capacity of the virus toexpress long sequence inserts when fused directly to orposttranslationally cleaved from NS1, the stop-start system can behighly advantageous compared to the incorporation of long sequences,i.e. of an internal ribosome entry site element. The stop-start codoncan be inserted at any position within the NS gene between the splicedonor and the splice acceptor site without modifying the nucleotidesequences of the functional splice sites.

In an alternative embodiment the stop-start codon is inserted at aposition wherein at least 4 nucleotides, more preferred at least 6nucleotides, (more preferred at least 8 nucleotides downstream) of the5″ splice donor site of the NS gene are expressed. The NS 5′ and 3′intron boundaries are defined as the cleavage site between the firstexon and the intron and the cleavage site between the intron and thesecond exon. In case of influenza A, the insertion of the start-stopcodon is placed at any position within the NS gene, although at least 10N-terminal amino acids of the NS1 protein, alternatively at least 12N-terminal amino acids of the NS1 protein are expressed. Alternatively,the heterologous open reading frame can also be at least partiallyoverlapping with the NS1 open reading frame.

In an embodiment of the invention the translation of the heterologousopen reading frame is initiated from an optimized translation initiationsequence, preferably the translation initiation sequence is a Kozakconsensus sequence (Kozak M., Nucleic Acids Research, 1984, 12,857-872). This consensus sequence can comprise at least part of thesequence CCRGCCAUGG, wherein R can be A or G (SEQ ID NO. 54). Positions−3 (i.e., 3 nucleotides upstream from the ATG codon) and +4 have thestrongest influence on translation (Kozak M., Nucleic Acids Research,1987, 15, 8125-8148). Thus, the consensus sequence can also be RXXAUGG,XXAUGG or RXXAUG.

Furthermore according to the invention the NS gene segment contains afunctional splice donor and/or acceptor splice site. According to theinvention the splice donor and acceptor sites of the NS gene areconsisting of the two nucleotides 3′ to the 5′ intron boundary and thetwo nucleotides 5′ to the 3′ intron boundary. Homology to U1 snRNA orpyrimidine stretch can also be tested and developed to improvefunctional splice sites.

According to a specific embodiment, the NS gene segment contains afunctional natural splice donor and acceptor splice site, i.e. thesplice donor and acceptor sites are kept as natural sites, i.e. thenucleotides are not modified by artificial techniques.

Any nucleotide modifications at the splice sites occurring naturally dueto modifications of influenza viruses based on environmental adaptationsor natural strain developments are natural modifications and do not fallunder the term synthetic or artificial modifications.

Alternatively, the sequences surrounding the splice donor and/orupstream of the acceptor site can be altered, Preferably, alteration ormodification can be performed within 3 nucleotides 5′ to the and/or 8nucleotides 3′ to the 5′ border of the NS intron, as well as 100nucleotides 5′ to the and/or 2 nucleotides 3′ to the 3′ border of the NSintron. This is preferably by introducing synthetic sequences in orderto modify splicing activity.

If e.g. insertion of a heterologous sequence increases NS intron size itmay be preferable to modify the sequences surrounding the splice donorand/or acceptor site in order to increase splicing efficacy and thusgenetic stability of the recombinant NS segment.

For example, it can be modified in that either the sequence surroundingthe splice donor site is altered to increase the homology to the 5′ endof the human U1 snRNA and/or the sequence upstream of the spliceacceptor site containing the branch point (Plotch et al. 1986, Proc NatlAcad Sci USA. 83:5444-8; Nemeroff et al. 1992, Mol Cell Biol. 12:962-70)and the pyrimidine stretch is replaced by a sequence that enhancessplicing of the NS segment.

For example, the sequence surrounding the 5′ splice site can be changedfrom

(as found in the PR8 NS segment, (SEQ ID. No 55) to

(nucleotides complementary to the 5′ end of the human U1 snRNA are shownin bold italic letters, the splice donor site is indicated by “/”, (SEQID. No 56).

In order to optimize splicing, the a preferred sequence introduced 5′ ofthe splice acceptor site comprises a lariat consensus sequence and apyrimidine stretch. For example, the sequence upstream of the syntheticsplice acceptor site can be as follows:

TACTAAC

GACAG/ (SEQ ID. No 57)

The lariat consensus sequence is underlined, the pyrimidine stretch isbold, the 3′ intron boundary is indicated by “/”.

In view of stability of the virus vector and the expression rate of theheterologous sequence it can be important to introduce thesynthetic/modified sequence containing a lariat consensus sequence and apyrimidine stretch at a specific position within the NS gene, e.g.directly upstream of the slice acceptor site.

Furthermore, it may be necessary to vary the distance between the lariatconsensus sequence and the pyrimidine stretch to modify the splicingrate of the NS segment (Plotch S. and Krug R., 1986, Proc. Natl. Acad.Sci., 83, 5444-5448; Nemeroff M. et al., 1992, Mol. Cell. Biol.,962-970).

In a preferred embodiment the replication deficient influenza virusaccording to the invention comprises a nucleotide sequence as shown inFIG. 1 (a-j) or is at least 96% homologous, alternatively at least 98%homologous.

In an additional embodiment, also a combination of at least tworeplication deficient influenza viruses according to the inventioncomprising at least one biologically active molecule or derivative orfragment thereof and at least one antigenic structure is claimed. Suchcombination comprising different heterologous sequences might beadvantageous in view of further increasing humoral as well as cellularimmunogenicity. For example, one of the vectors can contain a cytokineor fragment or derivative thereof like IL2 and a second virus vector cancomprise an antigenic peptide or polypeptide.

Alternatively the heterologous sequences can also comprise fusionproteins wherein cytokines or chemokines or fragments or derivativesthereof are fused to antigenic proteins or antigenic peptides or linkeddirectly or via a linker peptide to the NS1 protein derivative.

The present invention covers also a signal peptide comprising part ofthe N-terminal amino acids of an NS1 protein, for example 10-12 aminoacids of the N-terminus of the NS1 protein, and a signal peptide or partthereof fused to the C-terminus of said NS1 peptide. Said signal peptidecan consist of 8 to 30, preferably up to 50 amino acids.

The signal sequence can be derived from an antibody light chain,preferably from an Ig kappa chain, more preferably from mouse Ig kappachain. According to an alternative embodiment, the Ig Kappa chain cancomprise at least 10 amino acids, more preferred at least 12 aminoacids, for example comprising the sequence METDTLLLWVLLLWVPGSTGD (SEQID. No. 11) or METDTLLLWVLLLWVPRSHG (SEQ ID No. 82) or part thereof.

A vaccine formulation comprising the replication deficient influenzavirus vector according to the invention is also covered.

According to the invention the replication deficient influenza virus canbe used for the preparation of a medicament for therapeutic treatment inpatients, for example for the treatment of infectious diseases orcancer.

Methods of introduction include but are not limited to intradermal,intramuscular, intraperitoneal, intravenous, intranasal, epidural ororal routes. Introduction by intranasal routes is preferred.

In a preferred embodiment it may be desirable to introduce themedicament into the lungs by any suitable route. Pulmonaryadministration can also be employed, using e.g. an inhaler or nebulizeror formulate it with an aerosolizing agent.

The pharmaceutical preparation can also be delivered by a controlledrelease system, like a pump.

The medicament according to the invention can comprise a therapeuticallyeffective amount of the replication deficient virus and apharmaceutically acceptable carrier. “Pharmaceutically acceptable” meansapproved by regulatory authorities like FDA or EMEA. The term “carrier”refers to a diluent, adjuvant, excipient or vehicle with which thepreparation is administered. Saline solutions, dextrose and glycerolsolutions as liquid carriers or excipients like glucose, lactose,sucrose or any other excipients as known in the art to be useful forpharmaceutical preparations can be used. Additionally, also stabilizingagents can be included to increase shelf live of the medicament.

Preferably, a ready-to-use infusion solution is provided. Alternatively,the preparation can be formulated as powder which is solved inappropriate aqueous solutions immediately before application.

The amount of the pharmaceutical composition of the invention which willbe effective in the treatment of a particular disorder or condition willdepend on the nature of the disorder or condition, and can be determinedby standard clinical techniques. In addition, in vitro assays mayoptionally be employed to help identify optimal dosage ranges. Theprecise dose to be employed in the formulation will also depend on theroute of administration, and the seriousness of the disease or disorder,and should be decided according to the judgment of the practitioner andeach patient's circumstances. However, suitable dosage ranges foradministration are generally about 10⁴-5×10⁷ pfu and can be administeredonce, or multiple times with intervals as often as needed.Pharmaceutical compositions of the present invention comprising10⁴-5×10⁷ pfu of mutant replication deficient viruses can beadministered intranasally, intratracheally, intramuscularly orsubcutaneously Effective doses may be extrapolated from dose-responsecurves derived from in vitro or animal model test systems.

Furthermore, a vector comprising a nucleotide sequence coding for areplication deficient influenza virus according to the invention iscovered.

If a DNA vector is used, said vector is a transcription system for minussense influenza RNA. For example it can be a vector as used by Hoffmannet al., 2000, Proc Natl Acad Sci USA. 97:6108-13. Alternatively, also anRNA comprising the sequence coding for the inventive replicationdeficient virus can be used.

Method for producing the inventive replication deficient influenza viruscomprising the steps of: transfecting cells, preferably Vero cells, withat least one vector comprising the sequence for the inventive virus,incubating the transfected cells to allow for the development of viralprogeny containing the heterologous protein is of course also covered bythe invention.

Alternatively, a method for producing a replication deficient influenzavirus is also provided, comprising the steps of: transforming a cell,preferably a Vero cell, with a vector comprising a nucleotide sequencecoding for a replication deficient influenza virus according to theinvention preferably together with a purified preparation of influenzavirus RNP complex, infecting the selected cells with an influenza helpervirus, incubating the infected cells to allow for the development ofviral progeny and selecting transformed cells that express the modifiedNS gene and the heterologous sequence,

The foregoing description will be more fully understood with referenceto the following examples. Such examples are, however, merelyrepresentative of methods of practicing one or more embodiments of thepresent invention and should not be read as limiting the scope ofinvention.

EXAMPLES Example 1 Expression of Human Interleukin-2 From a SeparateOpen Reading Frame

A cDNA coding for human IL-2 was inserted into a modified NS segment ofthe influenza A strain Puerto Rico/8/34 that does not code for afunctional NS1 protein. The NS1 protein was terminated after amino acid21 by means of an artificially introduced Stop codon and thus doesneither contain the RNA binding domain nor the effector domain.

To allow IL-2 translation the artificially introduced NS1 stop codonoverlaps with the Start codon of IL-2 to give the sequence TAATG (SEQ IDNo. 81). Two constructs were generated (see FIG. 2).

In both constructs (deINS1-IL-2-10 and deINS-IL-2-11) the IL-2 cDNAincluding the overlapping Stop/start codon replaces nucleotides 90-345of the wild-type NS segment corresponding to amino acids 22-106 of theNS1 protein.

Construct deINS-IL-2-10 thus comprises the natural splice acceptor site,the natural branch point 20 nucleotides upstream of the splice acceptorsite (Plotch et al. 1986, Proc Natl Acad Sci USA. 83:5444-8; Nemeroff etal. 1992, Mol Cell Biol. 12:962-70) as well as the natural 11-nucleotidepyrimidine stretch of the wild-type NS segment. A lariat consensussequence (CTRAY or YNYYRAY) that is found 72 nucleotides upstream of the3′ splicing site in the wild-type NS segment is also present in thedeINS-IL-2-10 segment.

In addition, in the deINS1-IL-2-11 segment a synthetic sequence of 29nucleotides comprising a lariat consensus sequence followed by a 20-basepyrimidine stretch segment replaces nucleotides 361-525 of the wild-typeNS segment corresponding to amino acids 112-166 of the NS1 protein. Thusalso the natural branch point, the pyrimidine stretch as well as thelariat consensus sequence found 72 bases upstream of the 3′ splicingsite in the NS segment were replaced.

Furthermore, in both chimeric IL-2 NS segments the sequence downstreamof the 5′ intron boundary was changed to achieve 100% complementarity tothe 5′ end of the human U1 snRNA (i.e. /GTAGATTG as found in the wildtype NS segment was changed to GTAAGTAT). In addition a methionine foundin alternative reading frame at position 76 of the wild-type NS segmentwas changed to a valine.

Thus the amino acid sequence of the truncated NS1 protein isMDPNTVSSFQVSIFLWRVRKR (letters shown underlined in bold denote changesfrom the wild-type NS sequence, (SEQ ID No. 59).

Description of the deINS1-IL-2-10 segment as shown in FIG. 1 a: the ORFis consisting of the truncated NS1, i.e. the nucleotides 27-92; thehuman IL-2 ORF consists of nucleotides 92-553; The 5′ intron boundary islocated between nucleotides 56 and 57; the 3′ intron boundary is betweennucleotides 739 and 740 (SEQ ID No 1).

Description of the deINS1-IL-2-11 segment as shown in FIG. 1 b: the ORFof the truncated NS1 consists of nucleotides 27-92; the human IL-2 ORFconsists of nucleotides 92-553; the splice donor site is betweennucleotides 56 and 57; the splice acceptor site is between nucleotides603 and 604 (SEQ ID No 2);

Plasmid Constructions

As a backbone for construction of chimeric human Interleukin-2 NSsegments the plasmid pKW2000 was used. pKW2000 was obtained by deletingthe CMV promoter in pHW2000 (Hoffmann et al. 2000, Proc Natl Acad SciUSA. 97:6108-13). Thus upon transfection only vRNA is transcribed frompKW2000 derivatives.

DeINS1-IL-2-10 and deINS1-IL-2-11 segments were constructed by PCRstandard methods and cloned into pKW2000 to yield the plasmidspKW-deINS-IL2-10 and pKW-deINS-IL-2-11, respectively. Analogously, apKW2000 derivative containing the PR8 deINS segment (Garcia-Sastre etal. 1998, Virology. 252:324-30) was constructed (pKW-deINS1).

PA, PB1, PB2, HA, NA, M and NP segments derived from a Vero-cell adaptedinfluenza A H1N1 virus strain (GHB01) were cloned into pHW2000.

All plasmids were sequenced to ensure the absence of unwanted mutations.

Generation of Viruses

Vero cells were maintained in DMEM/F12 medium containing 10% foetal calfserum and 1% Glutamax-I supplement at 37° C.

For virus generation seven pHW2000 derivatives containing the segmentsPA, PB1, PB2, HA, NA, M and NP derived from GHBO1 as well as two proteinexpression plasmids coding for Influenza A PR8 NS1 (pCAGGS-NS1(SAM);(Salvatore et al. 2002, J Virol. 76:1206-12)) and NEP (pcDNA-NEP) wereused together with either pKW-deINS-IL-2-10, pKW-deINS-IL-2-11 orpKWdeINS1 for cotransfection of Vero cells. Following transfection, tosupport virus replication Vero cells were cultured in serum-free medium(Opti-Pro; Invitrogen) in the presence of 5 μg/ml trypsin. Three daysafter transfection 50-100% CPE was observed and rescued viruses werefrozen or further amplified on Vero cells. In addition chimeric IL-2expressing viruses were plaque purified once. After amplification onVero cells several plaques were frozen for further analysis.

The generated viruses are designated GHB-IL-2-10, GHB-IL-2-11 and GHB01.

Analysis of Interleukin-2 Expression

Vero cells were infected at a multiplicity of infection of 0.1 withGHB-deINS1, GHB-IL-2-10 or GHB-IL-2-11 and incubated for 16 h at 37° C.in serum-free medium in the presence of 1 μg/ml trypsin. Subsequently,foetal calf serum (final concentration 10%) as well as soy bean trypsininhibitor (final concentration 100 μg/ml) was added and incubation at37° C. was continued for another 24 h.

Supernatants were analysed for secreted IL-2 by ELISA.

IL-2 expression was found to be about 5-fold higher for the GHB-IL-2-10virus compared to the GHB-IL-2-11 virus (see FIG. 3). As expected, noIL-2 was detected in supernatants infected with GHBO1 virus lacking theIL-2 cDNA.

The human-IL2 expression level in Vero cells was approx. 2600 pg/ml inGHB-IL-2-10 and approx. 500 pg/ml GHB-IL-2-11. In contrast, theexpression level according to the state of the art was between 250-350pg/ml (Kittel et al., 2005, s. above).

Analysis of Virus Stability

Chimeric IL-2 influenza viruses obtained either directly aftertransfection or after one round of plaque purification were seriallypassaged five times on Vero cells. RNA was extracted using a ViralAmpkit (Qiagen) and reverse transcribed. Whole NS segments were PCRamplified and subjected to agarose gel electrophoresis to evaluate thepresence of deletions.

As shown in FIG. 4, deletion bands were found for all GHB-IL-2-10 virussamples regardless of plaque purification. In contrast, PCR productsobtained for the GHB-IL-2-11 virus samples migrated at the expected size(see FIG. 4).

Example 2 Expression of Human Interleukin-2 From the NS1 Open ReadingFrame

A cDNA coding for human IL-2 was inserted into a modified NS segment ofthe influenza A strain Puerto Rico/8/34 that does not code for afunctional NS1 protein. In contrast to example 1, the IL-2 cDNA wasdirectly fused to a truncated (12 amino acid) NS1 protein. Thus, IL-2 isexpressed from the NS1 open reading frame (see FIG. 1 c, deINS1-IL-2-14)

To allow IL-2 secretion, a cDNA coding for the mature IL-2 was fused tothe first 12 aa of the NS1 protein via a modified Ig kappa signalpeptide resulting in the following amino acid sequence:

(SEQ ID No. 60) MDPNTVSSFQVS-

- APTSSSTKKTQLQLEHLLLDLQMILNGINNYKNPKLTRMLTFKFYMPKKATELKHLQCLEEELKPLEEVLNLAQSKNFHLRPRDLISNINVIVLELKGSETTFMCEYADETATIVEFLNRWITFCQSIISTLT.

The first 12 amino acids of the above sequence correspond to thetruncated NS1 protein, the amino acids corresponding to the modifiedmouse Ig kappa signal peptide are depicted in italic bold letter, andthe remaining amino acid sequence corresponds to the mature human IL-2.

Description of the deINS1-IL-2-14 segment: ORF of the NS1-IgKappa-IL-2fusion: nucleotides 27-509; Splice donor site between nucleotides 56 and57; Splice acceptor site between nucleotides 559 and 560 (FIG. 1 c)

Virus generation and analysis of IL-2 expression was done as describedin example 1. The generated viruses was designated GHB-IL-2-14.

IL-2 expression levels were found to be about 17-times higher than forGHB-IL-2-11 (see FIG. 5). Thus, high level IL-2 expression from thetruncated NS1 open reading frame is feasible.

Example 3 Influence of the Sequence Surrounding the Splice Donor Site onIL-2 Expression

To analyse the influence of the sequence surrounding the splice donorsite on IL-2 expression, deINS1-IL-2-11 and deINS1-IL-2-14 were furthermodified.

DeINS1-IL-2-13 was constructed from deINS1-IL-2-11 by changing the 8nucleotides downstream of the 5′ intron boundary from

to

as found in the wild type PR8 NS segment (nucleotides complementary tothe 5′ end of the human U1 snRNA are shown in bold italic letters, the5′ intron boundary is indicated by “/”). The deINS1-IL2-13 sequence isshown in FIG. 1 d.

Similarly, deINS1-IL-2-21 was constructed from deINS1-IL-2-14 bychanging the sequence

to

(nucleotides complementary to the 5′ end of the human U1 snRNA are shownin bold italic letters, the 5′ intron boundary is indicated by “/”).

The deINS1-IL2-21 sequence is shown in FIG. 1 e.

Thus, in both constructs homology to the 5′ end of the U1 snRNA wasdecreased when compared to their progenitor constructs.

For deINS1-IL-2-13 the amino acid sequence for the truncated NS1 proteinis: MDPNTVSSFQVDCFLWRVRKR (SEQ ID NO. 61)

For deINS1-IL-2-21 the amino acid sequence for the NS1-IgK signalpeptide-IL-2 fusion protein is: MDPNTVSSFQV-FA

APTSSSTKKTQLQLEHLLLDLQMILNGINNYKNPKLTRMLTFKFYMPKKATELKHLQCLEEELKPLEEVLNLAQSKNFHLRPRDLISNINVIVLELKGSETTFMCEYADETATIVEFLNRWITFCQSIISTLT (SEQ ID NO. 62)

The first 11 amino acids of the above sequence correspond to thetruncated NS1 protein, the amino acids corresponding to the modifiedmouse Ig kappa signal peptide are depicted in italic bold letter, andthe remaining amino acid sequence corresponds to the mature human IL-2.

Viruses were generated and analysed for IL-2 expression as described inexample 1. The generated viruses were designated GHB-IL-2-13andGHB-IL-2-21. Genetic stability of the deINS1-IL-2-13 and deINS1-11-2-21segment was analysed after 5 consecutive passages on Vero cells asdescribed in example 1.

IL-2 expression levels were found to be higher for the respectiveconstructs that have a lower homology to the U1 sRNA around their splicedonor site (see FIG. 5).

Levels for GHB-IL-2-13 were found to be about 13-times higher than forthe corresponding virus that exhibits a high homology to the U1 snRNA(GHB-IL-2-13; 9,4 ng/ml versus 0,7 ng/ml; FIG. 5). Similarly, IL-2levels for GHB-IL-2-21 were found to be roughly 2,6-times higher thanfor GHB-IL-2-14 (31,1 ng/ml versus 12,1 ng/ml; FIG. 5).

Thus, by modifying the sequence around the NS splice donor site IL-2expression levels can be tuned.

For both viruses, deINS1-IL-2-13 and deINS1-Il-2-21 no deletion bandswere found after 5 consecutive passages indicating genetic stability.

Example 4 Expression of IL-2 From a Separate Open Reading Frame:Translation Initiation via a Kozak Consensus Sequence

The stop/start codon sequence in deINS1-IL-2-11 was replaced by a Kozakconsensus sequence (i.e. the TAATG was replaced with TAAGCCGCCACCATG;the stop and start codon are indicated in bold underlined letters, SEQID No. 63) to yield the segment deINS1-IL-2-17.

The deINS1-IL-2-17 nucleotide sequence is shown in FIG. 1 f.

Virus generation and analysis of IL-2 expression for GHB-IL-2-17 wasperformed as described in example 1. IL-2 expression levels were foundto be about twice as high as for GHB-IL-2-11 (data not shown).

Example 5 Expression of Human IL-15 From the NS1 Open Reading Frame

A cDNA coding for human IL-15 is inserted into a modified NS segment ofthe influenza A strain Puerto Rico/8/34 that does not code for afunctional NS1 protein. To allow secretion, the a cDNA encoding matureIL-15 is fused to a truncated (11 amino acid) NS1 ORF via a modifiedmouse Ig kappa signal peptide resulting in the following amino acidsequence: MDPNTVSSFQV-FA

NWVNVISDLKKIEDLIQSMHIDATLYTESDVHPSCKVTAMKCFLLELQVISLESGDASIHDTVENLIILANNSLSSNGNVTESGCKECEELEEKNIKEFLQSFVHIVQMFINTS (SEQ ID No. 69)

The first 11 amino acids of the above sequence correspond to thetruncated NS1 protein, the amino acids corresponding to the modifiedmouse Ig kappa signal peptide are depicted in italic bold letter, andthe remaining amino acid sequence corresponds to the mature human IL-15.

The resulting chimeric IL-15 NS segment is referred to asdeINS1-IL-15-21. The deINS1-IL-15-21 nucleotide sequence is shown inFIG. 1 g

Virus generation is performed as described in example 1.

IL-15 expression levels in the supernatants of infected Vero cells wereassessed by ELISA and were found to be in the range of 1-2 ng/ml.

Example 6 Expression of Human GM-CSF From the NS1 Open Reading Frame

A cDNA coding for human GM-CSF is inserted into a modified NS segment ofthe influenza A strain Puerto Rico/8/34 that does not code for afunctional NS1 protein. To allow secretion, the mature GM-CSF cDNA isfused to a truncated (11 amino acid) NS1 protein via a modified mouse Igkappa signal peptide resulting in the following amino acid sequence:MDPNTVSSFQV-FA

APARSPSPSTQPWEHVNAIQEARRLLNLSRDTAAEMNETVEVISEMFDLQEPTCLQTRLELYKQGLRGSLTKLKGPLTMMASHYKQHCPPTPETSCATQIITFESFKENLKDF LLVIPFDCWEPVQE(SEQ ID NO. 64)

The first 11 amino acids of the above sequence correspond to thetruncated NS1 protein, the amino acids corresponding to the modifiedmouse Ig kappa signal peptide are depicted in italic bold letter, andthe remaining amino acid sequence corresponds to the mature humanGM-CSF.

The resulting chimeric GM-CSF NS segment is referred to asdeINS1-GM-CSF-21. The deINS1-GM-CSF-21 nucleotide sequence is shown inFIG. 1 h

Virus generation is performed as described in example 1.

Example 7 Expression of Human CCL-3 From the NS1 Open Reading Frame

A cDNA coding for human CCL-3 (MIP-1alpha) is inserted into a modifiedNS segment of the influenza A strain Puerto Rico/8/34 that does not codefor a functional NS1 protein.

To allow secretion, the mature CCL-3 cDNA is fused to a truncated (11amino acid) NS1 protein via a modified mouse Ig kappa signal peptideresulting in the following amino acid sequence: MDPNTVSSFQV-FA

APLAADTPTACCFSYTSRQIPQNFIADYFETSSQCSKPSVIFLTKRGRQVCADPSEE WVQKYVSDLELSA(SEQ ID NO. 65)

The first 11 amino acids of the above sequence correspond to thetruncated NS1 protein, the amino acids corresponding to the modifiedmouse Ig kappa signal peptide are depicted in italic bold letter, andthe remaining amino acid sequence corresponds to the mature human CCL-3.

The resulting chimeric CCL-3 NS segment is referred to asdeINS1-CCL-3-21. The deINS1-CCL-3-21 nucleotide sequence is shown inFIG. 1 i

Virus generation is performed as described in example 1.

Example 8 Expression of Human CCL-20 From the NS1 Open Reading Frame

A cDNA coding for human CCL-20 (MIP-3alpha) was inserted into a modifiedNS segment of the influenza A strain Puerto Rico/8/34 that does not codefor a functional NS1 protein.

To allow secretion, the mature CCL-20 cDNA was fused to a truncated (11amino acid) NS1 protein via a modified mouse Ig kappa signal peptideresulting in the following amino acid sequence: MDPNTVSSFQV-FA

ASNFDCCLGYTDRILHPKFIVGFTRQLANEGCDINAIIFHTKKKLSVCANPKQTWVKYI VRLLSKKVKNM(SEQ ID NO. 66)

The first 11 amino acids of the above sequence correspond to thetruncated NS1 protein, the amino acids corresponding to the modifiedmouse Ig kappa signal peptide are depicted in italic bold letter, andthe remaining amino acid sequence corresponds to the mature humanCCL-20.

The resulting chimeric CCL-20 NS segment is referred to asdeINS1-CCL-20-21. The deINS1-CCL-20-21 nucleotide sequence is shown inFIG. 1 j

Virus generation is performed as described in example 1.

CCL-20 expression levels in the supernatants of infected Vero cells wereassessed by ELISA was found to be in the range of 25 ng/ml.

Example 9 Expression of Secreted Mycobacterium tuberculosis ESAT-6 Fromthe NS1 Open Reading Frame

A cDNA coding for mycobacterium tuberculosis ESAT-6 was inserted into amodified NS segment of the influenza A strain Puerto Rico/8/34 that doesnot code for a functional NS1 protein.

To allow secretion, an ESAT-6 cDNA was fused to a truncated (11 aminoacid) NS1 protein via a modified mouse Ig kappa signal peptide resultingin the following amino acid sequence: MDPNTVSSFQV-FA

MTEQQWNFAGIEAAASAIQGNVTSIHSLLDEGKQSLTKLAAAWGGSGSEAYQGVQQKWDATATELNNALQNLARTISEAGQAMASTEGNVTGMFA (SEQ ID NO. 70)

The first 11 amino acids of the above sequence correspond to thetruncated NS1 protein, the amino acids corresponding to the modifiedmouse Ig kappa signal peptide are depicted in italic bold letter, andthe remaining amino acid sequence corresponds to ESAT-6.

The resulting chimeric ESAT-6 NS segment is referred to asdeINS1-ESAT-6s-21. The deINS1-ESAT-6s-21 nucleotide sequence is shown inFIG. 1 k

Virus generation was performed as described in example 1.

Example 10 Intracellular Expression of Mycobacterium tuberculosis ESAT-6From the NS1 Open Reading Frame

A cDNA coding for mycobacterium tuberculosis ESAT-6 was inserted into amodified NS segment of the influenza A strain Puerto Rico/8/34 that doesnot code for a functional NS1 protein.

In contrast to example 9 an ESAT-6 cDNA was directly fused (i.e. withoutan amino acid sequence acting as a signal peptide) to a truncated (11amino acid) NS1 protein resulting in the following amino acid sequence:

(SEQ ID NO. 71) MDPNTVSSFQVFA

The first 11 amino acids of the above sequence correspond to thetruncated NS1 protein, while the amino acid sequence shown in italicbold letters corresponds to ESAT-6.

The resulting chimeric ESAT-6 NS segment is referred to asdeINS1-ESAT-6i-21. The deINS1-ESAT-6i-21 nucleotide sequence is shown inFIG. 1 l.

Virus generation was performed as described in example 1.

Example 11 Expression of IL-2 From the NS1 Open Reading Frame UsingAlternative Signal Peptide Sequences

The deINS1-IL2-21 segment (example 3) was modified by replacing thepartial mouse IgK signal peptide sequence with other sequences.

For deINS1-IL2-23 the amino acid sequence LLWVLLLWVPGSTG (SEQ ID No. 58)in deINS1-IL2-21 was replaced by the sequence WVLFILLLFLFLPRSHG (SEQ IDNo. 72) resulting in the amino acid sequence

(SEQ ID No. 73) MDPNTVSSFQVFAWVLFILLLFLFLPRSHG-APTSSSTKKTQLQLEHLLLDLQMILNGINNYKNPKLTRMLTFKFYMPKKATELKHLQCLEEELKPLEEVLNLAQSKNFHLRPRDLISNINVIVLELKGSETTFMCEYADETATIVEFLNRWITFCQSIISTLT.

The deINS1-IL2-23 nucleotide sequence is shown in FIG. 1 m.

For deINS1-IL2-24 the amino acid sequence LLWVLLLWVPGSTG (SEQ ID No. 58)in deINS1-IL2-21 was replaced by the sequence AGAALLALLAALLPASRA (SEQ IDNo. 74) which is derived from the human epidermal growth factor (hEGF)signal peptide (MRPSGTAGAALLALLAALCPASRA, (SEQ ID No. 75)) resulting inthe amino acid sequence

(SEQ ID No. 76) MDPNTVSSFQVFAAGAALLALLAALLPASRAAPTSSSTKKTQLQLEHLLLDLQMILNGINNYKNPKLTRMLTFKFYMPKKATELKHLQCLEEELKPLEEVLNLAQSKNFHLRPRDLISNINVIVLELKGSETTFMCEYADETATIVEFLN RWITFCQSIISTLT.

The deINS1-IL2-24 nucleotide sequence is shown in FIG. 1 n.

Virus generation was performed as described in example 1.

IL-2 expression levels in the supernatants of infected Vero cells wereassessed by ELISA.

Thus, the partial mouse IgK signal peptide can be replaced by othersequences acting as a signal peptide.

Example 12 Modification of Sequences Surrounding the Splice Donor andAcceptor Site Affects NS Splicing Efficiency

To analyse the influence of the sequences surrounding the intronboundaries on splicing efficiency deINS1-IL-2-10 (see example 1) wasfurther modified. DeINS1-IL-2-12 was constructed from deINS1-IL-2-10 bychanging the 8 nucleotides downstream of the 5′ intron boundary from

to

as found in the wild type PR8 NS segment (nucleotides complementary tothe 5′ end of the human U1 snRNA are shown in bold italic letters, thesplice donor site is indicated by “/”). Otherwise the deINS1-IL-2-12nucleotide sequence is identical to deINS1-IL-2-10.

Virus generation was done as described in example 1.

Genetic stability of the deINS1-IL-2-12 segment was analysed after 5consecutive passages as described in example 1. Clear deletion bandswere found (data not shown).

To analyse splicing efficacy, Vero cells were cotransfected with fourplasmids expressing PB1, PB2, PA and NP proteins along with a plasmidexpressing vRNA of deINS1-IL-2-10, deINS1-IL-2-11 (see example 1),deINS1-IL-2-12 or deINS1-IL-2-13 (see example 3).

24 hours later mRNA was extracted from transfected cells and analysedfor spliced and unspliced deINS1-IL-2 mRNA species by Real Time PCR.

The following table summarises the sequence modifications performedeither 3′ to the splice donor site or 5′ to the splice acceptor site aswell as genetic stability and IL-2 expression levels (IL-2 expressionfor deINS1-IL-2-10 and deLNS1-IL-2-12 are not given since both segmentsappeared genetically unstable).

segment delNS1- delNS1- delNS1- delNS1- IL-2-12 IL-2-10 IL-2-13 IL-2-11Sequence 3′ to wild-type modified wild-type modified splice donor siteSequence 5′ to 3′ wild-type wild-type modified modified splice acceptorsite Genetic stability negative negative positive positive IL-2expression na na 8 ng 700 pg

As shown in FIG. 7, deINS1-IL-2 mRNA splicing can be altered by eithermodifying the sequence surrounding the splice donor site or thesequences 5′ to the splice acceptor site.

It is also apparent, that increasing splicing efficiency above a certainthreshold necessary to achieve genetic stability reduces IL-2 expression(deINS1-IL-2-13 versus deINS1-IL-2-11).

Example 13 Expression of Human Interleukin-2 From a Separate OpenReading Frame of Influenza B

A cDNA coding for human IL-2 was inserted into a modified NS segment ofthe influenza B strain B/Vienna/33/06. The NS1 protein was terminatedafter amino acid 38 by means of an artificially introduced Stop codonand thus does neither contain the RNA binding domain nor C-terminaldomain of NS1.

To allow IL-2 translation the artificially introduced NS1 stop codonoverlaps with the Start codon of IL-2 to give the sequence TAATG. Aschematic expression scheme is given in FIG. 8. In this construct(ΔNS1-38IL2), the IL-2 cDNA including the overlapping Stop/start codonreplaces nucleotides 159-728 of the wild-type NS segment correspondingto amino acids 38-228 of the NS1 protein.

In this construct, a synthetic sequence of 29 nucleotides comprising alariat consensus sequence followed by a 20-base pyrimidine stretchsegment replaces the natural splice acceptor site plus the naturalpyrimidine stretch analogous to the influenza A constructdeINS1-IL-2-11.

Description of the ΔNS1-38IL2 segment as shown in FIG. 8: the ORF of thetruncated NS1 consists of nucleotides 45-158; the human IL-2 ORFconsists of nucleotides 161-619; the 5′ intron boundary is betweennucleotides 77 and 78; the 3′ intron boundary is between nucleotides 657and 658.

Generation of Plasmids and Viruses

Plasmids for influenza B Viruses were generated analogous to theinfluenza A plasmids using standard cloning techniques. HA and NAderived from a Vero-cell adapted influenza B/Thüringen/2/06 strain andPA, PB1, PB2, M and NP segments derived from a Vero-cell adaptedinfluenza B/Vienna/33/06 virus strain and were cloned into pHW2006. Allplasmids were sequenced to ensure the absence of unwanted mutations.

The IL2 expressing influenza virus was generated as described forinfluenza A and designated ΔNS1-38IL2.

Analysis of Virus Stability

Chimeric IL-2 influenza viruses obtained directly after transfectionwere serially passaged four times on Vero cells. RNA was extracted usinga ViralAmp kit (Qiagen) and reverse transcribed. Whole NS segments werePCR amplified and subjected to agarose gel electrophoresis to evaluatethe presence of deletions. PCR products obtained for the ΔNS1-38IL2virus samples after 1 and 4 passages migrated at the expected size,indicating that the IL2 expressing vector is stable.

Immunogenicity in Mice

To investigate the immunogenic potential, mice were immunized with1*10⁵TCID₅₀/mouse with wt influenza B Virus, ΔNS1-38IL2, ΔNS1-38 (acontrol Virus which was constructed similar to ΔNS1-38IL2 but withoutthe insertion of IL2) or PBS as a control. Four weeks post immunization,mice were challenged with 2*10⁵TCID₅₀/mouse of homologous influenza B wtvirus. Three days post infection, mice were sacrificed and viralreplication was investigated in lungs and nasal turbinates were. Micewhich were immunized with the wt influenza Virus were protected in lungsand noses whereas in the control mice immunized with PBS, viral titresof approximately 3 logs in both, nasal and lung tissues. At the dose of1*10⁵TCID50/mouse none of the mice immunized with ΔNS1-38 was protectedfrom wt influenza challenge manifesting nasal and lung tissuescomparable to the naïve animals. In contrast, no virus could be isolatedfrom any mouse immunized with virus ΔNS1-38IL2 at the same dose,indicating that all mice were protected.

1. Replication deficient influenza virus characterized in that itcomprises a) a modified NS segment coding for a NS1 protein comprisingat least one amino acid modification within positions 1 to 73 resultingin complete lack of its functional RNA binding and at least one aminoacid modification between position 74 and the carboxy-terminal aminoacid residue resulting in complete lack of its effector function and b)a heterologous sequence between a functional splice donor site andfunctional splice acceptor site inserted in the NS gene segment 2.Replication deficient influenza virus according to claim 1 characterizedin that it comprises at least 10 amino acids and preferably up to 14,preferably up to 30 amino acids of the N-terminus of the NS1 protein. 3.Replication deficient influenza virus according to any one of claim 1 or2 characterized in that amino acids 134 to 161 are deleted. 4.Replication deficient influenza virus according to any one of claim 1 or2 characterized in that amino acids 117 to 161 are deleted. 5.Replication deficient influenza virus according to any one of claims 2to 4 comprising a signal peptide or part thereof fused to the C-terminusof NS1 protein.
 6. Replication deficient influenza virus according toany one of claims 1 to 5 characterized in that the heterologous sequenceis expressed from the NS1 open reading frame.
 7. Replication deficientinfluenza virus according to any one of claims 1 to 5 characterized inthat the heterologous sequence is expressed from a separate open readingframe.
 8. Replication deficient influenza virus according to any one ofclaims 1 to 7 characterized in that the heterologous sequence isselected from the group consisting of biologically active proteins,antigens or derivatives or fragments thereof.
 9. Replication deficientinfluenza virus according to any one of claims 1 to 8 characterized inthat the heterologous sequence is a chemokine or cytokine or derivativeor fragment thereof.
 10. Replication deficient influenza virus accordingto any one of claims 1 to 9 characterized in that the heterologoussequence is derived from mycobacterium tuberculosis.
 11. Replicationdeficient influenza virus according to any one of claims 1 to 10characterized in that the heterologous sequence comprises a signalpeptide.
 12. Replication deficient influenza virus according to claim 11characterized in that the signal peptide is derived from an antibodylight chain, preferably from an Ig kappa chain, more preferably frommouse Ig kappa chain.
 13. Replication deficient influenza virusaccording to claim 12 characterized in that the Ig kappa signal peptidecomprises at least 10 amino acids, more preferred at least 12 aminoacids.
 14. Replication deficient influenza virus according to any one ofclaim 12 or 13 characterized in that the Ig kappa signal peptidecomprises the sequence METDTLLLWVLLLWVPGSTGD (SEQ ID No. 11) orMETDTLLLWVLLLWVPRSHG (SEQ ID No. 82) or part or derivatives thereof. 15.Replication deficient influenza virus according to any one of claims 1to 14 characterized in that the heterologous sequence comprises a fusionprotein of a biologically active protein and an antigen.
 16. Replicationdeficient influenza virus according to any one of claims 1 to 15characterized in that the heterologous sequence is selected from thegroup consisting of IL2, GM-CSF, IL15, MIP 1 alpha and MIP 3 alpha,ESAT-6 or a derivative or fragment thereof.
 17. Replication deficientinfluenza virus according to any one of claims 1 to 16 characterized inthat the translation of said NS1 protein is terminated by at least oneSTOP codon and expression of said heterologous sequence is reinitiatedby a START codon.
 18. Replication deficient influenza virus according toany one of claims 1 to 17 characterized in that the heterologous openreading frame is at least partially overlapping with the NS1 openreading frame.
 19. Replication deficient influenza virus according toany one of claims 1 to 18 characterized in that translation of theheterologous open reading frame is initiated from an overlappingSTOP/START codon sequence.
 20. Replication deficient influenza virusaccording to claim 19 characterized in that the overlapping START/STOPcodon is TAATG (SEQ ID. No. 81) or UAAUG (SEQ ID No. 53). 21.Replication deficient influenza virus according to any one of claims 1to 20 characterized in that translation of the heterologous open readingframe is initiated from an optimized translation initiation sequence,preferably a Kozak consensus sequence.
 22. Replication deficientinfluenza virus according to any one of claims 1 to 21 containing analtered sequence downstream of the splice donor site and/or upstream ofthe splice acceptor site in the NS segment.
 23. Replication deficientinfluenza virus according to any one of claims 1 to 22 characterized inthat the heterologous sequence is secreted from the infected cell. 24.Replication deficient influenza virus according to any one of claims 1to 23 with a sequence as shown in SEQ ID Nos 1 to 10, 67, 68 or with atleast 98% homology therewith.
 25. Combination of at least tworeplication deficient influenza viruses according to any one of claims 1to 24 comprising at least one biologically active molecule or derivativeor fragment thereof and at least one antigenic structure.
 26. Vaccinecomprising a replication deficient influenza virus according to any oneof claims 1 to
 24. 27. Use of a replication deficient influenza virusaccording to any one of claims 1 to 24 for the preparation of amedicament for therapeutic treatment in patients.
 28. Use of areplication deficient influenza virus according to any one of claims 1to 24 for the preparation of a medicament for the tumor treatment inpatients.
 29. Vector comprising a nucleotide sequence coding for areplication deficient influenza virus according to any one of claims 1to
 24. 30. Method for producing a replication deficient influenza virusaccording to any one of claims 1 to 24, comprising the steps of:transfecting cells, preferably Vero cells, with at least one vectoraccording to claim 29, incubating the transfected cells to allow for thedevelopment of viral progeny containing the heterologous protein. 31.Method for producing a replication deficient influenza virus accordingto any one of claims 1 to 24, comprising the steps of: transforming acell, preferably a Vero cell, with a vector according to claim 29preferably together with a purified preparation of influenza virus RNPcomplex, infecting the selected cells with an influenza helper virus,incubating the infected cells to allow for the development of viralprogeny and selecting transformed cells that express the modified NSgene and the heterologous sequence,
 32. Method for the creation of areplication deficient influenza virus according to any one of claims 1to 24, comprising the steps of: transfecting a cell line, preferably aVero cell line, with a DNA vector comprising a modified NS gene free offunctional RNA binding domain and a heterologous sequence insertedbetween a functional splice donor site and the splice acceptor site ofthe NS gene, selecting transfected cells that express the modified NSgene and the heterologous sequence, infecting the selected cells with adesired influenza virus, incubating the infected cells to allow for thedevelopment of viral progeny containing the heterologous protein,selecting and harvesting said viral progeny containing the heterologousprotein.
 33. The method according to claim 29, characterized in that theDNA vector is a transcription system for minus sense influenza RNA. 34.The method according to claim 29 or 30, characterized in that said viralprogeny is further combined with a pharmaceutically acceptable carrierfor use as a vaccine.
 35. Fusion protein comprising between 10 and 30amino acids of the N-terminus of an NS1 protein, a heterologous sequenceand a signal peptide fused to the C-terminus of said NS1 peptide. 36.Fusion protein according to claim 32 characterized in that the signalpeptide consists of 8-50 amino acids.
 37. Fusion protein according toany one of claim 32 or 33 characterized in that the signal peptide isderived from an antibody light chain, preferably from an Ig kappa chain,more preferably from mouse Ig kappa chain or a derivative thereof. 38.Fusion protein according to any one of claims 35 to 37 characterized inthat the Ig kappa signal peptide comprises at least 10 amino acids, morepreferred at least 12 amino acids.
 39. Fusion protein according to anyone of claims 35 to 38 characterized in that the Ig kappa signal peptidecomprises the sequence METDTLLLWVLLLWVPGSTGD (SEQ ID No. 11) orMETDTLLLWVLLLWVPRSHG (SEQ ID No. 82) or part or derivatives thereof.